Congestive heart failure (CHF) is a debilitating and progressive disease that causes a heart to pump less efficiently over time. Typically, the heart has been weakened by an underlying problem, such as clogged arteries, high blood pressure, a defect in heart muscles or heart valves, or some other medical condition. Many symptoms and conditions associated with heart failure can be treated, but to date in many cases the underlying impairment of the heart cannot.
One characteristic of heart failure is remodeling of the heart—that is, physical change to the size and shape of the heart and thickness of the heart wall. In many cases the wall of the left ventricle thins and stretches in places. The thinned portion of the myocardium is typically functionally impaired and other portions may grow or thicken to compensate.
Typically, the heart enlarges as heart failure progresses, which seems to be the result of the body trying to compensate for weakening heart muscles. The heart can become so enlarged that the heart can no longer provide an adequate supply of blood to the body. As a result, individuals afflicted with congestive heart failure often experience shortness of breath and fatigue even with minimal activity. Also, as the heart enlarges, the heart valves may not adequately close, which further reduces the heart's ability to supply blood to the body.
Drug therapies have been developed to treat individuals afflicted with congestive heart failure. A drug regimen of beta blockers, diuretics, and angiotensin-converting enzyme inhibitors (ACE inhibitors) aims to improve the effectiveness of the heart's contractions and slow CHF progression. Although drug therapy for heart failure can improve the quality of life and also modestly prolong survival, it is well established that many of the currently available approaches do not represent satisfactory long-term treatment options for a large number of patients.
Once the disease progresses to the point that medication is no longer effective, the currently preferred options are a heart transplant or a ventricular assist device (VAD). Approximately 550,000 new cases of CHF are diagnosed in the United States alone every year. Of these, at least 75,000 individuals are candidates for a heart transplant. But more than 50,000 men and women die every year waiting for a heart transplant because of a lack of donor hearts.
Only a few hundred VADs are implanted in the US each year. VAD use is limited because device implant surgery is highly invasive and complicated. Management of pump volume or pressure is difficult. VAD surgery adds insult to the heart because of the required surgical connections into the ventricle and aorta. But the largest contributor to complications from VAD implantation is the required direct interface of the device with the patient's blood. This can lead to clotting, strokes, and infection.
In addition to drugs, transplants, and VADs, heart failure has been treated with cardiac jackets or restraint devices. These basically consist of flexible material wrapped around the heart. A cardiac jacket is fitted around an enlarged heart to physically limit expansion of the heart during diastole. This may prevent further enlargement of the heart.
Improved methods and devices for treating heart failure and other cardiac diseases are needed.